Hi, i'll try and make this as easy to understand for my first post.
I'm using ArcMap 9.2.
Ok, I've created a NDVI raster for a large map I have so the date ranges from -1 -> 1.
I also have a shapefile as a seperate layer.
What i'm trying to do is use the shapefile as a mask to cut away the excess map that I don't need.
I can do this using the extraction tool (spatial analyst -> extraction -> extract by mask), the clip tool (data management -> raster -> clip) or by using the analysis mask under the spatial analyst toolbar analyst mask (spatial analyst -> options -> general) and then evaluating my NDVI layer in the raster calculator).
However, my problem is that when I complete this on my NDVI layer, the remaining, useful, output raster has data ranging from -0.3 -> 0.6 (not the original -1 -> 1).
How do i stop the data changing as such so that it remains as the same data range as the orginal layer.
Am I simply not ticking the correct box somewhere along the line?
Your help would be appreciated, thanks!
